There has been a constant effort to use technology to substitute images for reality. Since the Renaissance inventions of perspective and trompe l'oeil to the present day's “virtual reality,” there has been a constant effort to find ways to convince the viewer that an image of an object is the object itself.
Great strides were made by Dr. Thomas Furness inventor of the head mounted display (HMD). The HMD, although cumbersome, was a breakthrough in that it harnessed the ability of the computer to generate images on the basis of gestures and actions and allowed a fabricated image to automatically change in response to physical actions of the viewer in manner that mimicked the way the real world responds to such actions. Furness thus demonstrated the importance of interaction and feedback in enhancing the communication experience.
The HMD has a number of limitations, most prominent of which is the manner in which the viewer's head in blindly encased within a helmet. Another shortcoming is the weight (and subsequent fatigue and intrusiveness) of the display system. Removal of the helmet and wearing the display as glasses exchanges the intrusion of the helmet for intrusiveness of the real world upon viewer—still reducing the effectiveness of the illusion of being immersed in the displayed world. This exchanged of one form of intrusion for another only slightly reduces the degree to which a viewer rendered effectively blind to the real world.
In all cases of virtual reality displays (with exception of those that create a virtual exit pupil), since a display in located in close proximity to the eye, the viewer suffers problems resulting from the dissociation of eye vergance (where objects seem some distance from the observer) from accommodation (where the eye is forced to stretch the macula to focus on a screen in close proximity in order to focus the image onto the retina.)
To address the limitations of the head-mounded display, Dr. Furness further created the virtual retinal display (VRD) described in a series of patents ranging from WO 94/09472A1 to the present day U.S. Pat. No. 6,639,570B2. Others with patents in this area include Intel Corporation U.S. Pat. No. 6,474,816B2, the Entertainment Design Workshop LLC U.S. Pat. No. 6,454,411B1, and companies inventing applications to place atop the VRD such as Virtual-Eye.com's vision testing U.S. Pat. No. 6,386,706B1 or into specific devices such as Swisscom Mobile AG EP 1198957B1 for mobile devices and Be Intellectual Property Inc.'s incorporation into aviation masks. The virtual retinal display system is a system displayed in a manner bypassing the eye's lenses, and instead projected an image onto the retina artificially designed to be like one focused by the eye onto the retina. This display addressed the problem of disjunction of vergance and accommodation in traditional displays. This created new problems and challenges in the form of finding a means of scanning extremely small images onto the retina (essentially treating the retina like a micro-cathode of a television and substituting a laser for electron beam). The research and concepts of Furness and others associated with the University of Washington stimulated work on the scanning problem by the Microvision Company on miniature scanning systems such as U.S. Pat. No. 6,140,979A which is further covered in patents up to the present day.
Individuals have been successful in finding a number of means for improving the speed and flexibility of scans, most common is that typical of color television displays where three separate scanning beams are used to generate a single, colored image. In patent application U.S. 2001/0022566 A1 (Yoji Okazaki) describes the use of three separate lasers to produce the three different wavelengths for a color display. A method taught by IBM patent GB 2 297 422 A (John Beeteson and Andrew Ramsay Knox) is a form of pixel astigmatism, where pixels to allow to be of nonuniform size to facilitate painting a larger area in a given amount of time. Another recently issued patent U.S. Pat. No. 6,628,446 B1 (Arie Shahar and Nira Schwartz)—typical of a class of solutions—teaches using multiple beams and lenses rotating at standard speed or double speed. A patent U.S. Pat. No. 6,184,969 B1 (James L. Fergason) teaches using active and passive dithering to enhance the display, getting around the limitations of the scan by providing additional pixel enhancement as appropriate. Another method is taught by GB 2 284 902 A (Paul May, Michael Geraint Robinson, Craig Tombling, Edward Peter Raynes) where multiple electro-optical liquid crystal display devices are integrated to allow additional flexibility in image pixel addressability.
All the display solutions continue to be limited by the concept of creating images by scanning, that is by changing the elements of the image in a spatially and temporally sequential manner. More to the point, the real world requires a standard fixing the spatial location of a image pixels of particular size and to be refreshed at fixed times and for fixed duration and display shave sought to ameliorate the obvious constraints of scan display systems while maintaining some continuity with existing standards.